Abstract This project focuses on two themes: 1) elucidation of novel mechanisms that drive guanine nucleotide binding (G)-protein signaling and tumorigenesis and 2) investigation of individual and coordinated roles of cell adhesion proteins in regulating cell morphology, force transmission and cell motility. Our work on G-proteins is centered on RAS and heterotrimeric G?-proteins. Recent findings from our lab challenge a long-held dogma in the field that oncogenic activation of G-proteins is primarily driven by defects in nucleotide cycling. However, it is becoming increasingly clear that codon and residue specific activating mutations in G-proteins can drive tumorigenesis by distinct mechanisms. In other words, not all activating mutations are created equal. We propose studies aimed at understanding how residue specific activating mutations uniquely alter G-protein structure, nucleotide cycling, protein recognition and signaling, that may be key to developing precision medicine approaches to antagonize G-protein mediated tumorigenesis. Our lab has also uncovered novel mechanisms of G-protein activation by post-translational modification and pH regulation. We propose highly integrated multidisciplinary structural, biochemical and cell biology approaches to interrogate the role of these novel posttranslational modifications in signaling and tumorigenesis. Our second theme is focused on the cell adhesion proteins, vinculin and metavinculin. These cell adhesion proteins are isoforms that play a key role in regulation of cell morphology, differentiation, force transmission and directed cell migration. We propose studies to experimentally examine new models for vinculin and metavinculin-mediated filamentous actin assembly and membrane insertion, conduct cellular studies to elucidate how metavinculin coordinately regulates vinculin function, and elucidate how metavinculin cardiomyopathy mutations dysregulate contractile force in heart disease. We will also investigate how vinculin and metavinculin engage filamentous actin in a force dependent manner to regulate directed cell motility.